In the medical field, patients frequently require supplemental oxygen due, for example, to a diminished lung function caused by a disease or disorder. Continuous flow devices are known that provide a supply of such supplemental oxygen to a patient. However, there are undesirable effects of such devices, such as an inefficient use of the oxygen supply since the oxygen is not needed continuously, and this results in increased medical costs to the patient.
It is known to use pressure sensors in connection with devices that provide automatic delivery of oxygen for medical purposes. However, the electronic signals produced by such pressure sensors, and this even includes those having built-in temperature compensation, often exhibit too much drift to enable use of the sensor in providing a precise, timed delivery of oxygen. In this regard, the signal drift occurring in pressure sensors commonly used in supplying medical oxygen, which is typically between 0.05% and 2%, can be significant relative to a 1 PSI full-scale measurement range provided by such sensors. Although more sensitive pressure sensors for such medical applications are currently available, such sensors are fragile and thus easily damaged, and are relatively costly as well.
Thus, a need exists in the industry for a device that accurately provides supplemental oxygen to a patient only when the oxygen is needed, i.e., at the time the patent inhales, without the drawbacks found in controlled devices that are now available, and particularly without the adverse effects caused by signal drift associated with the pressure sensor used to detect patient inhalation and activate the flow control system. Such a device should also be portable and include automatic built-in correction for temperature drift and signal offset present in the signal processing circuitry to accurately delivery the supplemental oxygen. While supplemental oxygen control devices of the types known in the art are satisfactory for many applications, they do not meet the above-identified needs, nor do they in general provide the various advantages present in the invention as described below.